The use of magnetic fields in the casting of heavy metals, such as aluminum is well known. In one known process, called "electromagnetic casting", an alternating magnetic field forces the aluminum away from the walls of the casting pit, so that no contact is provided between the metal and the mold during cooling, which produces aluminum ingots with smoother, cleaner surfaces.
This technique also has been applied to continuous casting wherein the conventional chill mold is replaced by a magnetic field which exerts a radial force on the molten metal. When the metal solidifies, it forms a column, which is lowered continuously at the same time as molten metal is supplied to the mold.
Problems arise, however, in the commercial application of such casting techniques. In particular, a rolling action often is experienced at the meniscus of the melt as a result of unbalanced magnetic forces acting on this area, which leads to surface imperfections in the cooled metal. In addition, metals heavier than aluminum, such as copper and iron, are difficult or impossible to process by such techniques, because of the much higher magnetic fields involved.